It is well known in the art of jewelry-making to attach the two ends of a small chain worn around the neck or arms by means of a clasp. Such clasps are also used to attach security chains to jewelry.
The clasp which is most known and used commercially comprises a hollow ring in which is mounted a plunger which slides inside the ring and is biased by means of a spring, also located inside the ring, to close a small open arc formed in the ring. This kind of clasp, however, has major disadvantages. For example, the plunger and the spring, which are located inside the ring, do not receive sufficient ventilation and corrode easily due to the humidity of the skin. The ring itself is also subject to be easily flattened or twisted out of shape. The result is that the plunger becomes stuck and the clasp stays half or fully open, leading possibly to the loss of a valuable piece of jewelry.
Another type of clasp used in jewelry has the form of pincers having a jaw provided with several pairs of teeth which overlap each other to partially surround the ring at the end of the chain. This ring can easily be caught in a single pair of teeth and, if too much tension is applied to the chain, the pair of teeth may break.